Troubleshooting

Autodetection failed

During the start of MPD, it tries to autodetect your set-up and configure output and volume control accordingly. Though this mostly goes well, it will fail for some systems. It may help to tell MPD specifically what to use as output and mixer control. If you copied /etc/mpd.conf over from /etc/mpd.conf.example as mentioned above, you can simply uncomment:

Note: in case of permission problems when using ESD with MPD run this as root:

# chsh -s /bin/true mpd

MPD hangs on first startup

This is a common error that's caused by corrupt mp3 tags.
Here is an experimental way to solve this issue.
Requirements:

kid3

easytag

This method is very tedious, especially with a huge database. Just as a baseline it took 2.5h to fix a 16Gb DB.

Easy Tag

The purpose of easytag here is that easytag detects the error in the tags, but like MPD it hangs and dies. The trick here is that easy tags actually tells you what file is causing the problem on the status bar.
Before starting easytag make sure to have a terminal close to be ready to kill easy tag to avoid a hang. Once you are ready, on the tree view select the directory where all your music is located. By default easytag starts to search all subdirectories for mp3 files. Once you notice that easytag stopped scanning for songs, make note of the culprit and kill easytag.

KID3

Here's where kid3 comes in handy. With kid3 go to the offending song and rewrite one of the tags. then save the file. This should force kid3 to rewrite the whole tag again fixing the problem with MPD and easy tag hanging.

Repeat this procedure until your music library is done.

Cannot connect to mpd: host "localhost" not found: Temporary failure in name resolution

Cannot connect to MPD (with ncmpcpp), if you are disconnected from network. Solution is disable IPv6 or add line to /etc/hosts

::1 localhost.localdomain localhost

Other issues when attempting to connect to mpd with a client

Some have reported being unable to access mpd with various clients, for example seeing errors like these:

To make the changes have effect, restart mpd (e.g. /etc/rc.d/mpd restart, if it is a global configuration).

High CPU usage with ALSA

When using MPD with ALSA, users may experience MPD taking up lots of CPU (around 20-30%). This is caused by most sound cards supporting 48kHz and most music being 44kHz, thus forcing MPD to resample it. This operation takes lots of CPU cycles and results into high usage.

For most users the problem should be solved by telling MPD not to use resampling by adding auto_resample "no" into audio_output-part of /etc/mpd.conf. This will degrade quality slightly, however.

mpd.conf

audio_output {
type "alsa"
name "My ALSA Device"
auto_resample "no"
}

Although it may not give as drastic a speedup, enabling mmap may still speed things up:

mpd.conf

audio_output {
type "alsa"
name "My ALSA Device"
use_mmap "yes"
}

Some users might also want to tell dmix to use 44kHz as well. More info about tuning performance of your MPD can be found on the MPD wiki